Impaired sperm motility in HIV-infected men: an unexpected adverse effect of efavirenz?

STUDY QUESTION: Are antiretroviral therapies associated with semen alterations in HIV-infected men? SUMMARY ANSWER: Antiretroviral regimens that included the non-nucleosidic reverse transcriptase inhibitor efavirenz were associated with a significant impairment of sperm motility, whereas regimens without efavirenz were not associated with significant semen changes. WHAT IS KNOWN ALREADY: Semen alterations including decreased ejaculate volume and sperm motility have been reported in HIV-infected men. The hypothesis ascribing reduced sperm motility to damages induced in sperm mitochondria by nucleosidic (or nucleotidic) reverse transcriptase inhibitors (NRTIs) has not been confirmed in HIV-infected patients and the effects of antiretroviral treatments on semen parameters remain unclear. STUDY DESIGN, SIZE, DURATION: This case-control study compared semen characteristics across 378 HIV-1 infected patients receiving different antiretroviral regimens or never treated by antiretroviral drugs, in whom an initial semen analysis was done between 2001 and 2007. PARTICIPANTS/MATERIALS, SETTING, METHODS: The patients were partners from serodiscordant couples requesting medical assistance to procreate safely. Their status with regard to antiretroviral therapy at the time of semen analysis was categorized as follows: 1/ never treated patients (n = 66); 2/ patients receiving NRTIs only (n = 49); 3/ patients receiving a NRTIs + protease inhibitor (PI) regimen (n = 144); 4/ patients receiving a NRTIs + non-nucleosidic reverse transcriptase inhibitor (NNRTI) regimen (n = 119). Semen parameters were assessed through standard semen analysis. Additional analyses included measurement of sperm motion parameters using computer-assisted semen analysis, seminal bacteriological analysis, seminal biochemical markers and testosterone plasmatic levels. All analyses were performed in the Cochin academic hospital. The data were analyzed through multivariate analysis. MAIN RESULTS AND THE ROLE OF CHANCE: Sperm motility was the only semen parameter which significantly varied according to treatment status. The median percentage of rapid spermatozoa was 5% in the group of patients receiving a regimen including efavirenz versus 20% in the other groups (P < 0.0001). Accordingly, sperm velocity was reduced by about 30% in this group (P < 0.0001). The role of chance was minimized by the strict definition and the size of the study population, which included a large enough group of never treated patients, the controlled conditions of semen collection and analysis, the multivariate analysis, the specificity and the high significance level of the observed differences. LIMITATIONS, REASONS FOR CAUTION: The design of the study did not allow demonstrating a causal link between exposure to efavirenz and sperm motility. WIDER IMPLICATIONS OF THE FINDINGS: As efavirenz is widely used in current antiretroviral therapy, these findings may concern many HIV-infected men wishing to have children. This justifies further assessment of the consequences on fertility of the exposure to efavirenz. Moreover, the possibility of common cellular impacts underlying adverse effects of efavirenz in sperm cells and neurons deserved investigation. STUDY FUNDING/COMPETING INTERESTS: No external funding was used for this study. None of the authors has any conflict of interest to declare.

Low immunogenicity of quadrivalent meningococcal vaccines in solid organ transplant recipients.

Immunization against meningococcal disease is recommended for solid organ transplant (SOT) recipients at high risk for meningococcal disease or travelling to an endemic country. However, the immunogenicity of meningococcal vaccines has not been studied in this population. We analyzed the immune response of quadrivalent (against Neisseria meningitidis serogroups A, C, Y, and W) polysaccharidic non-conjugate and conjugate meningococcal vaccines in kidney- and liver-transplant patients using bactericidal assays against the targeted serogroups. Upon vaccination with a non-conjugate (n = 5) or a conjugate vaccine (n = 10), respectively, 40% and 50% of patients were able to mount an immune response, achieving at least the threshold correlated with protection defined as human serum bactericidal antibody titers of ≥4. Responders showed only partial and low responses (titers ≤64), thus predicting a rapid decline in bactericidal response. Only 1 patient developed a booster response to preexisting immunity. Our data argue for the need of additional measures for SOT recipients, when they are at risk of meningococcal disease.

2012/13 influenza vaccine effectiveness against hospitalised influenza A(H1N1)pdm09, A(H3N2) and B: estimates from a European network of hospitals.

While influenza vaccines aim to decrease the incidence of severe influenza among high-risk groups, evidence of influenza vaccine effectiveness (IVE) among the influenza vaccine target population is sparse. We conducted a multicentre test-negative case-control study to estimate IVE against hospitalised laboratory-confirmed influenza in the target population in 18 hospitals in France, Italy, Lithuania and the Navarre and Valencia regions in Spain. All hospitalised patients aged ≥18 years, belonging to the target population presenting with influenza-like illness symptom onset within seven days were swabbed. Patients positive by reverse transcription polymerase chain reaction for influenza virus were cases and those negative were controls. Using logistic regression, we calculated IVE for each influenza virus subtype and adjusted it for month of symptom onset, study site, age and chronic conditions. Of the 1,972 patients included, 116 were positive for influenza A(H1N1)pdm09, 58 for A(H3N2) and 232 for influenza B. Adjusted IVE was 21.3% (95% confidence interval (CI): -25.2 to 50.6; n=1,628), 61.8% (95% CI: 26.8 to 80.0; n=557) and 43.1% (95% CI: 21.2 to 58.9; n=1,526) against influenza A(H1N1) pdm09, A(H3N2) and B respectively. Our results suggest that the 2012/13 IVE was moderate against influenza A(H3N2) and B and low against influenza A(H1N1) pdm09.

Persistence of yellow fever vaccine-induced antibodies after solid organ transplantation.

Immunization using live attenuated vaccines represents a contra-indication after solid organ transplantation (SOT): consequently, transplant candidates planning to travel in countries where yellow fever is endemic should be vaccinated prior to transplantation. The persistence of yellow fever vaccine-induced antibodies after transplantation has not been studied yet. We measured yellow-fever neutralizing antibodies in 53 SOT recipients vaccinated prior to transplantation (including 29 kidney recipients and 18 liver recipients). All but one (98%) had protective titers of antibodies after a median duration of 3 years (min.: 0.8, max.: 21) after transplantation. The median antibody level was 40 U/L (interquartile range: 40-80). For the 46 patients with a known or estimated date of vaccination, yellow-fever antibodies were still detectable after a median time of 13 years (range: 2-32 years) post-immunization. Our data suggest there is long-term persistence of antibodies to yellow fever in SOT recipients who have been vaccinated prior to transplantation.

The follow-up of patients with postoperative infection of the spine.

The follow-up of patients with postoperative infection of the spine required a multidisciplinary teamwork under the guidance of the spine surgeon and the infectious disease (ID) specialist. During follow-up, the spine surgeon has to ensure the absence of neurological, mechanical and implant-related complications using clinical parameters and different imaging modalities. The ID physician has to give particular attention to antimicrobial efficacy and toxicity, especially during the first weeks when patients necessitate high-dose intravenous treatment.

Zinc transporter (ZnT)8(186-194) is an immunodominant CD8+ T cell epitope in HLA-A2+ type 1 diabetic patients.

AIMS/HYPOTHESIS: Anti-zinc transporter (ZnT)8 autoantibodies are commonly detected in type 1 diabetic patients. We hypothesised that ZnT8 is also recognised by CD8(+) T cells and aimed to identify HLA-A2 (A*02:01)-restricted epitope targets. METHODS: Candidate epitopes were selected by ZnT8 plasmid DNA immunisation of HLA-A2/DQ8 transgenic mice and tested for T cell recognition in peripheral blood mononuclear cells of type 1 diabetic, type 2 diabetic and healthy participants by IFN-γ enzyme-linked immunospot. RESULTS: White HLA-A2(+) adults (83%) and children (60%) with type 1 diabetes displayed ZnT8-reactive CD8(+) T cells that recognised a single ZnT8(186-194) (VAANIVLTV) epitope. This ZnT8(186-194)-reactive fraction accounted for 50% to 53% of total ZnT8-specific CD8(+) T cells. Another sequence, ZnT8(153-161) (VVTGVLVYL), was recognised in 20% and 25% of type 1 diabetic adults and children, respectively. Both epitopes were type 1 diabetes-specific, being marginally recognised by type 2 diabetic and healthy participants (7-12% for ZnT8(186-194), 0% for ZnT8(153-161)). CONCLUSIONS/INTERPRETATION: ZnT8-reactive CD8(+) T cells are predominantly directed against the ZnT8(186-194) epitope and are detected in a majority of type 1 diabetic patients. The exceptional immunodominance of ZnT8(186-194) may point to common environmental triggers precipitating beta cell autoimmunity.

Immunogenicity and safety of the influenza A H1N1v 2009 vaccine in cancer patients treated with cytotoxic chemotherapy and/or targeted therapy: the VACANCE study.

BACKGROUND: Influenza vaccination is recommended to cancer patients undergoing chemotherapy, but vaccine coverage remains low. During the 2009 influenza pandemic, French recommendations were to vaccinate immunocompromised patients with two doses of adjuvanted vaccine. This study aimed to evaluate vaccine immunogenicity in cancer patients receiving chemotherapy. PATIENTS AND METHODS: VACANCE is a prospective open-label study that evaluated the immunogenicity and safety of two doses of AS03A-adjuvanted H1N1v vaccine in cancer patients receiving cytotoxic and/or targeted therapies. Serum haemagglutination-inhibited antibody titres against influenza A H1N1v were measured at days 1, 21, and 42, to estimate the proportion of participants with antibody titres ≥ 1 : 40 [seroprotection rate (SPR)], the efficacy of seroconversion, and factors that increased the geometric mean titre. RESULTS: Sixty-five patients were included. At baseline, 5% of patients had vaccine strain titres of specific haemagglutination inhibition antibodies that were ≥ 1 : 40. After one and two doses of vaccine, SPRs were 48% and 73%, respectively, and seroconversion rates were 44% and 73%, respectively. Vaccine-related adverse events were mild to moderate. CONCLUSIONS: A single dose of AS03-adjuvanted A/H1N1 vaccine triggered a low immune response in cancer patients on chemotherapy depending on their treatment type and frequency. Two doses are needed for these cancer patients.

Heterologous prime boost COVID 19 vaccination.

Heterologous prime boost vaccination is a primary vaccination with different vaccines, most often from different vaccine platforms. It combines the immunological properties of the different vaccines and thereby induces humoral, cellular and, in some cases, mucosal response. For Covid prevention, it has been used in primary vaccination, due to safety issues and in boosters. We have evaluated some articles reporting on the results of this type of vaccine, and demonstrating its usefulness.

Low immunogenicity of seasonal trivalent influenza vaccine among patients receiving docetaxel for a solid tumour: results of a prospective pilot study.

BACKGROUND: Patients receiving cytotoxic therapy for solid tumours are at risk of severe influenza. However, few data are available regarding the immunogenical efficacy of influenza vaccine in these patients. METHODS: In this prospective study, 25 patients with breast (n=13) or prostate (n=12) cancer received a trivalent inactivated influenza vaccine along with docetaxel (Taxotere) administration. The influenza virus type A and B antibody titres were measured using haemagglutinin inhibition (Garten et al, 2009) before and 21 days after the vaccination. Seroconversion rate was defined as the percentage of patients with an increase in the serum titres ≥ 4 after vaccination. RESULTS: Median age was 65 years (range: 33-87 years); 52% were females. Seroconversion rates were low: 28% (95% CI: 23.1-33.3) for H1N1, 8% (95% CI: 7.7-8.3) for H3N2 and 16% (95% CI: 7.7-25) for the B strain. The geometric mean titres ratios were 2.16 (H1N1), 1.3 (H3N2) and 1.58 (B). No serious adverse event (AE) related to the vaccine was reported. All the reported AE were from mild-to-moderate intensity. CONCLUSION: In the patients receiving docetaxel for solid tumours, influenza vaccine triggers an immune response in only one third. Strategies using more immunogenic influenza vaccines must be evaluated in such patients.

Pharmacokinetics and diffusion into sputum of oseltamivir and oseltamivir carboxylate in adults with cystic fibrosis.

Oseltamivir is a prodrug of oseltamivir carboxylate (OC), a neuraminidase inhibitor used for treatment and prevention of influenza. The pharmacokinetics of these 2 compounds were investigated after a single 75-mg oseltamivir dose in 6 patients with cystic fibrosis (CF). Means ± standard deviations of the area under the curve from time zero to infinity (AUC) were 173 ± 58 µg · h/liter for oseltamivir and 2,256 ± 394 µg · h/liter for OC. The concentrations of OC in sputum 4 to 6 h and 22 to 26 h after the intake ranged from 4.1 to 62.2 µg/liter. The AUC of OC was approximately 30% lower than and significantly different from published values for volunteers. On the basis of the present results and because the anti-A/H1N1 influenza virus efficacy of OC is related to its AUC/50% effective concentration (EC(50)) ratio, an increase in the oseltamivir unitary dose could be considered for the treatment of influenza in CF patients. This should nevertheless be confirmed by a controlled pharmacokinetic study performed on a larger number of patients.

Comparative effectiveness of continuing a virologically effective first-line boosted protease inhibitor combination or of switching to a three-drug regimen containing either efavirenz, nevirapine or abacavir.

OBJECTIVES: To compare virological effectiveness in patients who continued on a virologically successful first-line boosted protease inhibitor (PI)-containing combination antiretroviral therapy (cART) regimen or who switched to a PI-free cART including efavirenz, nevirapine or abacavir. METHODS: From the French Hospital Database on HIV, we selected 439 patients with undetectable viral load (VL) on a first-line boosted PI-containing cART regimen who switched to a PI-free combination including efavirenz, nevirapine or abacavir. Each of these patients was matched with three patients who continued to take their first-line cART regimen, on the basis of gender, age, CD4 cell count, VL, date of cART initiation and the duration of VL undetectability. Time to virological failure (VF) was analysed with Kaplan-Meier curves and Cox models. RESULTS: The 12 month probabilities of VF were 3.7% and 5.7% in non-switch and switch patients, respectively, and 3.9%, 7.2% and 9.0% in patients switching to efavirenz-, nevirapine- and abacavir-containing cART, respectively. After adjustment, only patients switching to abacavir-containing cART had a higher risk of VF than non-switch patients (adjusted hazard ratio, 1.99; 95% confidence interval, 1.05-3.79). CONCLUSIONS: Switching from a virologically successful first-line boosted PI-containing cART regimen to a non-nucleoside reverse transcriptase inhibitor-containing cART regimen containing either efavirenz or nevirapine is virologically safe, while switching to abacavir-containing cART should be avoided.

High levels of serum hepatitis B virus DNA in patients with 'anti-HBc alone': role of HBsAg mutants.

It remains unclear how the detection of hepatitis B core antibody (anti-HBc) in the absence of hepatitis B surface antigen (HBsAg) and antibody (anti-HBs) should be interpreted and whether all patients with this pattern need to be tested for hepatitis B virus (HBV)-DNA. This study aimed at reassessing the significance of 'anti-HBc alone' in unselected sera referred to the clinical laboratory and determining whether significant HBV viraemia can be found in this setting. Of the 6431 patients tested for HBsAg, total anti-HBc and anti-HBs in a Paris hospital over a 1-year period, 362 (5.6%) had 'anti-HBc alone' (24.8% of anti-HBc-positive patients). Only 11 of the 362 sera (3.0%) were found to be false positive. One patient was in the resolving phase of acute hepatitis B. HBV-DNA was detected in 10 of 362 (2.8%) patients, using a commercial standardized assay (threshold: 350 IU/mL). Viral loads exceeded 10(4) copies/mL in 6 of 10 patients. Mutations in the HBsAg immunodominant region were identified in seven of the viraemic patients. HBsAg was detected in only two cases when retested by one of the latest, multivalent assays. Neither human immunodeficiency virus nor hepatitis C virus serostatus distinguished between patients with and without HBV-DNA. In conclusion, 'anti-HBc alone' should be considered a risk marker for a so-called 'false occult' HBV infection with significant viraemia. Indeed, results in this hospital population indicate that a small proportion of patients with 'anti-HBc alone' have high viral loads, revealing the occurrence of infection with HBV mutants that escape detection even by multivalent HBsAg assays.

Characteristics of human metapneumovirus infection in adults hospitalized for community-acquired influenza-like illness in France, 2012-2018: a retrospective observational study.

OBJECTIVES: To describe the prevalence, clinical features and complications of human metapneumovirus (hMPV) infections in a population of adults hospitalized with influenza-like illness (ILI). METHODS: This was a retrospective, observational, multicenter cohort study using prospectively collected data from adult patients hospitalized during influenza virus circulation, for at least 24 h, for community-acquired ILI (with symptom onset <7 days). Data were collected from five French teaching hospitals over six consecutive winters (2012-2018). Respiratory viruses were identified by multiplex reverse transcription polymerase chain reaction (RT-PCR) on nasopharyngeal specimens. hMPV + patients were compared with hMPV- patients, influenza+ and respiratory syncytial virus (RSV)+ patients using multivariate logistic regressions. Primary outcome was the prevalence of hMPV in patients hospitalized for ILI. RESULTS: Among the 3148 patients included (1449 (46%) women, 1988 (63%) aged 65 and over; 2508 (80%) with chronic disease), at least one respiratory virus was detected in 1604 (51%, 95% confidence interval (CI) 49-53), including 100 cases of hMPV (100/3148, 3% 95% CI 3-4), of which 10 (10%) were viral co-infection. In the hMPV + patients, mean length of stay was 7 days, 62% (56/90) developed a complication, 21% (14/68) were admitted to intensive care unit and 4% (4/90) died during hospitalization. In comparison with influenza + patients, hMPV + patients were more frequently >65 years old (adjusted odds ratio (aOR) = 3.3, 95% CI 1.9-6.3) and presented more acute heart failure during hospitalization (aOR = 1.8, 95% CI 1.0-2.9). Compared with RSV + patients, hMPV + patients had less cancer (aOR = 0.4, 95% CI 0.2-0.9) and were less likely to smoke (aOR = 0.5, 95% CI 0.2-0.9) but had similar outcomes, especially high rates of respiratory and cardiovascular complications. CONCLUSIONS: Adult hMPV infections mainly affect the elderly and patients with chronic conditions and are responsible for frequent cardiac and pulmonary complications similar to those of RSV infections. At-risk populations would benefit from the development of antivirals and vaccines targeting hMPV.

Does enfuvirtide increase the risk of bacterial pneumonia in patients receiving combination antiretroviral therapy?

BACKGROUND: Pooled analysis of the TORO comparative clinical trial data sets showed a significantly higher incidence rate (IR) of bacterial pneumonia (BP) among patients treated with enfuvirtide-containing combination antiretroviral therapy (ENF-cART) than in those treated with other cART regimens. OBJECTIVES: To examine the possible impact of ENF-cART on the risk of BP. METHODS: From the French Hospital Database on HIV, we selected two groups of patients among cART-treated patients who were prescribed a new cART regimen during the period 2001-2006, when their CD4 counts were <350 cells/mm(3). The ENF-cART and cART groups consisted of 1220 and 9374 patients, respectively. Poisson regression models were used to quantify the relationship between ENF-cART therapy and the risk of BP. RESULTS: At baseline the median CD4 counts were 100 and 211 cells/mm(3) and the median plasma viral load (pVL) values were 60 276 and 2702 copies/mL in the ENF-cART and cART groups, respectively. The respective BP IRs were 0.65 [95% confidence interval (CI) 0.25-1.06] and 0.31 (95% CI 0.25-0.38) cases per 100 person-years. After adjustment for age, the HIV transmission group, the time period, co-trimoxazole prophylaxis, and stratified CD4 cell counts and pVL values, we found that the BP risk ratio was not increased by enfuvirtide treatment (relative rate 1.39; 95% CI 0.46-4.13). In contrast, lower CD4 cell counts and higher pVL values were significantly associated with a higher risk of BP. CONCLUSIONS: ENF-cART is not associated with a significantly higher risk of BP than other cART regimens, although the value of the adjusted risk and the upper limit of the CI do not allow us to exclude a small increased risk.

Risk factors for major infections in Wegener granulomatosis: analysis of 113 patients.

OBJECTIVE: To characterise major infectious complications and analyse potential risk factors in patients with Wegener granulomatosis (WG). METHODS: Data from 113 patients with WG (69 male) followed at least once between January 1984 and March 2006 in our internal medicine department, were analysed retrospectively. RESULTS: A total of 35 patients (mean (SD) age at WG diagnosis: 50.2 (13.05) years) developed 53 major infections. Infections were: bronchopneumonias (n = 19), herpes zoster recurrences (n = 9), cellulitis (n = 4), prostatitis (n = 4), spondylodiscitis and septic arthritis (n = 3), digestive tract infections (n = 2), Enterococcus faecalis or Staphylococcus aureus septicaemia (n = 2), viral hepatitis B reactivations (n = 2), post transfusion HIV infection with fatal cerebral toxoplasmosis, oesophageal candidiasis, disseminated herpes simplex and cytomegalovirus infection, cytomegalovirus retinitis, herpetic keratitis, herpetic stomatitis, Serratia sp. node suppuration and fever resolving under broad spectrum antibiotics (n = 1 each). Half of the major infectious episodes occurred within 3 years after WG diagnosis. Eight (7%) patients died, with two (2%) infection-related deaths. Patients diagnosed with WG before 1996 had a significantly higher rate of infection than those diagnosed later (48% vs 24%, p = 0.02). Cyclophosphamide and corticosteroids were independently associated with significantly higher risk of major infection (p<0.05 and <0.001, respectively). All patients treated since 1993 received antipneumocystosis prophylaxis. CONCLUSION: Cyclophosphamide and corticosteroids were associated with higher risk of infection. Despite systematic cotrimoxazole prophylaxis, major infections, mostly bronchopneumonias and herpes zoster recurrences, were still common in the course of WG.

Factors influencing influenza-vaccination in adults under immunosuppressive therapy for a systemic inflammatory disease.

OBJECTIVE: The aim of this study was to evaluate flu vaccination rates and influencing factors in patients with systemic inflammatory diseases. METHODS: All patients presenting with a systemic inflammatory disease and taking immunosuppressants, who were hospitalized or had consulted in our internal medicine department between January 2 and 31, 2006, were included in the study. The information concerning flu vaccination was collected with a standardized form. RESULTS: One hundred and thirty-seven patients (mean age 53.1+/-17.6years; 40 [29%] male patients) were included: 39 (28%) had received flu vaccination in 2005 including 14 (16.7%) of the 84 patients with no other indication for flu vaccination than IS-induced immunodepression and 25 (47.2%) of the 53 patients with other flu vaccination indication(s) (p<0.001). The most frequent reasons for non-vaccination were: absence of physician recommendation (58%), fear of adverse effects (35%) and concern on vaccine clinical effectiveness (5%). The vaccination rate was significantly higher (49%) among patients who remembered having received a voucher from the French National Health Insurance Agency versus 18% among those who did not (OR=4.2 [95%CI, 1.92-9.19] p<0.05). This correlation remained significant after adjustment for confounding factors in a logistic regression model. CONCLUSION: Influenza-vaccination coverage is low in patients receiving immunosuppressive therapy for systemic inflammatory diseases. We have to increase the influenza-vaccination coverage in this population.

[Vaccinations for the traveling adult solid organ transplant recipient (excluding hematopoietic stem cell transplant recipients)]. / Vaccinations du voyageur adulte transplanté d'organes (à l'exclusion des receveurs de cellules souches hématopoïétiques).

Progress in transplantation technique has offered a growing number of solid organ transplant recipients the opportunity to travel to tropical and low-income countries. The issue of vaccine-preventable diseases is a challenging question in immunocompromised patients including those with solid organ transplant. Since the response to vaccines is weakened in case of chronic organ failure, candidates should be vaccinated early in the course of the disease. Clinicians should implement a vaccinal strategy until the patient is scheduled for transplantation and monitor its efficacy by serological assays. Live attenuated vaccines (such as yellow fever, measles-mumps-rubella, or chicken pox) are contra-indicated in solid organ transplant recipients and, when indicated, should be administered prior to transplantation, particularly in foreign-born patients highly likely to visit friends and relatives in endemic areas. Vaccinations for transplant recipients considering international travel should be realized according to the risk of acquiring vaccine-preventable diseases but also on both tolerance and immune response which are affected by degree and duration of immunosuppression, comorbidities, and type of organ transplanted. Routine and specific vaccinations for solid organ transplant recipients, as well as travel-related vaccination (such as hepatitis A, typhoid, meningococcal meningitis, rabies, tick-born encephalitis, Japanese encephalitis, and cholera) should be considered during a specific pretravel medical consultation. However, vaccination should be avoided in the 6 months following transplantation when patients are usually receiving the highest doses of immunosuppressive drugs. In this comprehensive review, we provide vaccination schedules based on published studies and guidelines for vaccination of solid organ transplant recipients.

[History and principles of vaccination]. / Histoire et principes de la vaccination.

INTRODUCTION: Vaccination constitutes a major advance in the prevention of infectious diseases. The principle of vaccination is to induce protection against a pathogen by mimicking its natural interaction with the human immune system. The vaccine reduces the risk of complications and mortality following subsequent exposure to an infectious agent. STATE OF THE ART: In this review we recall the history of vaccination as well as the basic immunological principles underlying the composition of vaccines and the response to vaccination. In this way, vaccines induce the immune system to produce an immunological memory based on T and B lymphocytes in order to produce a rapid and effective response to exposure to the targeted pathogen. OUTLOOK: The improvement of existing vaccines and the discovery of new vaccines requires an understanding of the immunological principles of vaccination. Great challenges remain, particularly in terms of target pathogens for future vaccine candidates and also the acceptance of vaccination. CONCLUSION: Understanding the principles of vaccination allows development of vaccines and the control of infectious diseases.

Barriers and motivations for participation in preventive vaccine clinical trials: Experience of 5 clinical research sites.

Recruitment in preventive vaccine trials (PVT) is challenging due to common barriers to clinical research and lack of vaccine confidence. Identifying determinants of participation can help to improve recruitment. A prospective survey was conducted in 5 French clinical investigational sites. People asked to participate in a PVT were given a questionnaire whether they decided to participate or not in the trial. A total of 341 people answered the survey: 210 accepting and 131 declining to participate in a PVT. Acceptors were significantly younger (38.5 vs 54.9 years old), more likely to be involved in early phase trials, had a higher level of education (p < 0.005) and a significantly better general opinion concerning vaccines (92.3% versus 72.3%, p < 0.005) compared with those who declined. Factors associated with acceptance or refusal were evaluated in 224 people in the 4 sites where both groups were included. In a multivariate analysis, three factors: older age, having heard about PVT through multiple sources and financial incentives were significantly associated with refusal to participate in the PVT. A generally favourable opinion of vaccines was associated with acceptance. The main motivation for participation was altruism (93.2%) whereas fear of side effects was at the forefront of the barriers (36.6%). Information given by the physician was a key point for decision-making in 70.2% of those who accepted. In brief, vaccine hesitancy may decrease recruitment in PVTs; reinforcing altruism and quality of information given are key points in acceptance of participation in PVT.